Solve issues with arrow functions containing void expression

Author: ondrejmirtes

src/Analyser/NodeScopeResolver.php

@@ -1843,7 +1843,7 @@ static function () use ($scope, $expr): MutatingScope {
 
 			$arrowFunctionScope = $scope->enterArrowFunction($expr);
 			$nodeCallback(new InArrowFunctionNode($expr), $arrowFunctionScope);
-			$this->processExprNode($expr->expr, $arrowFunctionScope, $nodeCallback, $context);
+			$this->processExprNode($expr->expr, $arrowFunctionScope, $nodeCallback, ExpressionContext::createTopLevel());
 			$hasYield = false;
 
 		} elseif ($expr instanceof ErrorSuppress) {

src/Rules/Functions/ArrowFunctionReturnTypeRule.php

@@ -7,6 +7,7 @@
 use PHPStan\Node\InArrowFunctionNode;
 use PHPStan\Rules\FunctionReturnTypeCheck;
 use PHPStan\Type\ObjectType;
+use PHPStan\Type\VoidType;
 
 /**
  * @implements \PHPStan\Rules\Rule<\PHPStan\Node\InArrowFunctionNode>
@@ -36,10 +37,16 @@ public function processNode(Node $node, Scope $scope): array
 		$returnType = $scope->getAnonymousFunctionReturnType();
 		$generatorType = new ObjectType(\Generator::class);
 
+		$originalNode = $node->getOriginalNode();
+		$isVoidSuperType = (new VoidType())->isSuperTypeOf($returnType);
+		if ($originalNode->returnType === null && $isVoidSuperType->yes()) {
+			return [];
+		}
+
 		return $this->returnTypeCheck->checkReturnType(
 			$scope,
 			$returnType,
-			$node->getOriginalNode()->expr,
+			$originalNode->expr,
 			'Anonymous function should return %s but empty return statement found.',
 			'Anonymous function with return type void returns %s but should not return anything.',
 			'Anonymous function should return %s but returns %s.',

tests/PHPStan/Rules/Functions/data/arrow-functions-return-type.php

@@ -15,3 +15,18 @@ public function doFoo(int $i)
 	}
 
 }
+
+class Bar
+{
+
+	public function doFoo(): void
+	{
+
+	}
+
+	public function doBar(): void
+	{
+		fn () => $this->doFoo();
+	}
+
+}

tests/PHPStan/Rules/Methods/data/arrow-function-bind.php

@@ -38,3 +38,23 @@ public function fooMethod(): Foo
 	}
 
 }
+
+class BazVoid
+{
+
+	public function doFoo(): void
+	{
+
+	}
+
+	public function doBar(): void
+	{
+		$this->doBaz(fn () => $this->doFoo());
+	}
+
+	public function doBaz(callable $cb): void
+	{
+
+	}
+
+}